Electronic components such as ICs (semiconductor components with integrated circuits) are usually tested for their functionality before they are mounted on printed circuit boards, for example, or used otherwise. The components to be tested are contacted by an automatic handling machine, usually called a “handler”, with contacting devices which in particular are in the form of contact bases, and are in electrical contact with a test head of a test device. After the end of the test process, the components are removed from the contacting devices by means of the handler, and sorted depending on the test result.
To hold and contact the components, handlers usually have plungers, i.e. longitudinally movable piston-like holding units, which can move back and forth and which can hold the components by means of a vacuum, in particular by applying a suction force. After the components have been placed, the plungers are brought within the handler into a position in which they can be moved forward on a straight path towards contacting devices, until the components come into contact with the contacting devices. After the test processes are carried out, the components are removed from the test head by means of the plunger, and positioned so that they can be removed from the handler via a discharge station and sorted depending on the test result.
To be able to carry out the tests under predetermined temperature conditions, it is also known to bring the components to predetermined temperatures before the test process. These temperatures can be, for example, in a range from −60° C. to +200° C.
The temperature of the components is usually controlled in a convective and/or conductive manner in a heat-insulated temperature control chamber, which can be arranged inside or outside the handler. In this case, multiple components are brought to the desired temperature simultaneously inside the temperature control chamber, before they are put onto the plungers and moved forward by them to the contacting devices. A disadvantage here is that in the time between the heating and the contacting of the components, or during the contacting of the components, heat losses occur, with the result that at the time of the test, the components are no longer at the precise setpoint temperature. The individual components which have been temperature controlled together in the temperature control chamber can also have different temperatures. The components may also lose electrical power during the electrical test.
From U.S. Pat. No. 5,977,785 A, a plunger according to the preamble of claim 1 is known. The plunger there has a head piece with a plurality of suction heads and a heat conducting body in the form of a contact plate which is arranged separately from the suction heads, and which can be heated or cooled by means of a hot or cold fluid. The sucked-in components rest against the contact plate and can be temperature controlled thereby. The temperature-controlled fluid is fed to the contact plate and taken away from it in closed circuits. However, a disadvantage is that the head piece is of complex construction and therefore must be relatively large, since the feed and take-off lines for the temperature-controlled fluid take up a relatively large amount of space and the contact plate must also be correspondingly large. For very small electronic components or for arrangements in which a plurality of plunger heads must be arranged closely next to one another, this known plunger head is unsuitable.
The invention is based on the object of creating a plunger of the above-mentioned kind, with which tests of electronic components can be carried out under predetermined temperature conditions as precisely as possible. The plunger should also be simply constructed and have a small overall size in the head region, so that it is suitable even for small components.
According to the invention, the suction head is fed through the heat conducting body. By way of the heat conducting body according to the invention, there is a very quick and intense transfer of heat from the heat conducting body to the component via heat conduction. Owing to its large surface area and the material it is made of, the temperature of the heat conducting body itself can be controlled extremely quickly using a fluid, which preferably consists of a gas, in particular clean air or nitrogen. The fluid can thus be conveyed from the interior of the handler or via fluid lines of the plunger to the heat conducting body. Depending on whether the components are to be tested at low temperature, ambient temperature or high temperature, the heat conducting body, and thus the component, is either cooled, kept at ambient temperature or heated. Because the temperature of the components is controlled directly at the plunger head, the temperature of the component which is held on the plunger can be controlled while it is being delivered to the assigned contacting device, and even during the test process, so that heat losses during the delivery movement and during the test process do not occur, or at least can be minimised. It is thus possible to control the temperature of the component in a very precise manner. The head piece can also be simply constructed and have a small overall size, so that the plunger can not only be used for large components, but also for very small ones.
According to an advantageous embodiment, the heat conducting body comprises a central axial through-opening, through which the suction head is guided. The contact surface between the heat conducting body and the component is thus kept extremely large so the temperature of the component can be controlled particularly effectively. A plurality of decentralised through-openings may also be provided in the heat conducting body, through each of which a suction head penetrates.
According to an advantageous embodiment, the plunger head comprises a retaining base which supports the sucked-in component and has an axial passage, in which the heat conducting body is arranged around the suction head or heads. In this embodiment the retaining body and heat conducting body are thus different parts, which simplifies production. Furthermore, it is therefore also possible for the heat conducting body and the retaining base to be made of different materials and to thus match these materials in an optimal manner to their respective applications. For example, the retaining base may be made of an electrically non-conductive material, in particular a plastics material, whilst the heat conducting body may be made of a particularly effective heat conducting metal. Alternatively however, it is also possible for the retaining base itself to be configured as a heat conducting body, i.e. for the retaining base to be configured in such a way that some regions of the retaining base, which contact the component, conduct heat particularly well in particular, a retaining base of this type may have fins or pins on its rear side which enlarge its surface and over which fluid flows.
According to an advantageous embodiment, the heat conducting body is held resiliently relative to the retaining base, in particular so as to be resiliently displaceable in the axial direction relative to the retaining base. Even if the size or shape of the components differs, it is thus ensured that they rest as flat as possible against the heat conducting body in order to ensure a good level of heat conduction.
It is particularly advantageous for the heat conducting body to be tiltably arranged relative to the longitudinal axis of the plunger. Even if the connecting legs (pins) of the component are not completely uniformly curved owing to tolerances, and the body of the component is tilted slightly out of its intended position or if the legs rest on supporting strips (lead backers) of the retaining base, complete surface contact of the body of the component against the heat conducting body is thus also ensured.
According to an advantageous embodiment, the heat conducting body consists of a disc-shaped body with fins projecting therebeyond, the disc-shaped body comprising a flat front face which can be contacted with the component, and the fins projecting rearwards beyond the disc-shaped body. The heat conducting body can thus be configured in a particularly compact manner, it also being possible to use extremely long fins which project rearwards into a fluid guide channel and which enable a particularly good transfer of heat from the fluid to the heat conducting body.
According to an advantageous embodiment, the retaining base comprises fluid guide recesses in its rear side, which open into the axial passage in the retaining base so at the rear side of the retaining base conveyed fluid can be guided towards the heat conducting body arranged in the axial passage in a targeted manner. It can thus be easily ensured that the greatest possible amount of fed, possibly temperature-controlled fluid flows directly over the heat conducting body, controlling the temperature of said body in a particularly effective manner.
According to an advantageous embodiment, the heat conducting body is displaceably guided by bolts extending in an axial direction and having a bolt head with a front face at their front end, which front face forms an axial stop for the component, and having a rear face which forms an axial stop for the heat conducting body. The heat conducting body is thus expediently pushed forward by springs which are arranged around the bolts. The heat conducting body is thus held resiliently and flexibly in the retaining base in a relatively simple and compact manner.